Material-saving container cap and associated container neck

ABSTRACT

A material savings container cap comprising a circular flat top having a perimeter, an annular segmented container cap wall, each separated segment of container wall descending from a different portion of the perimeter of the top, the container cap wall having an internal screw thread for interlocking with a container wall of the container neck wherein an angle of threading to the container cap wall is between approximately thirty degrees and approximately forty-five degrees. The container neck wall has an external screw thread having an angle to the container neck wall of approximately thirty degrees. The internal screw thread always points towards an inner surface of the top of the cap and towards an axis of rotation of the cap. In the container neck wall the external screw thread always points away from an opening of the container and away from an axis of rotation of the container neck.

TECHNICAL FIELD

This invention relates to container caps and their associated containernecks, and more particularly such container caps and associatedcontainer necks wherein the container caps achieve a significantmaterial saving.

BACKGROUND OF THE INVENTION

In the manufacturing process, the cost of raw materials is a basic andsignificant cost. Processes or methods that can eliminate portions ofthe cost of raw materials are valuable and much sought after. In themanufacturing of containers having screw-on container caps, the materialconstituting the actual container cap is a raw material that is usuallythought of as a fixed cost that cannot be reduced other than by a changein material.

In the manufacturing process, the manufacturer is expected to meetcertain achievement specifications. For example, in the case of acontainer cap that screws on to a container neck, the manufacturer isexpected to achieve a certain degree of tightening force with a certainamount of reliability. The manufacturer is also expected to achievethese results within a specified cost parameter.

Thus the threading on the cap and container neck must achieve a certaintightness needed to securely enclose the container and to do so withincost parameters defined by a third party.

It would be very advantageous to be able to achieve the same degree oftorque from the container cap without having to spend the same amount ofmoney for the raw material associated with the container cap itself andits associated container neck.

A container cap that does not contain the interlocking screw threaddesign form of the present invention will use superfluous material.

Known container caps are complete cylinders in that they have materialforming the cap wall running continuously around the wall of thecontainer cap without interruption. Prior art container caps alsocontain a threading having a cross-section that is “V” shaped.

Normally, it would be assumed that interrupting the wall of thecontainer cap by having segments separated by spaces would undermine theforce generated by the threading on the container cap and would make thethreading slip apart of a mating relationship with the threading on theneck. It is also assumed that were there to be separate segments of acontainer cap wall these segments would be forced to be spread open bythe force of the tightening.

It would be advantageous to have a container cap with reduced materialin which the segments of materials would not spread apart from the forceof the tightening and which would not cause the threading thereon toslip from its mating relationship.

The present invention achieves this and many other advantages.

SUMMARY OF THE PRESENT INVENTION

A material savings container cap and associated container neck ispresented wherein the material savings container cap is comprised acircular flat top having a perimeter, an annular segmented container capwall, each separated segment of container wall descending from adifferent portion of the perimeter of the top, the container cap wallhaving an internal screw thread design for interlocking with a containerwall of the container neck wherein an angle of a threading to thecontainer cap wall is between approximately thirty and forty fivedegrees. The container neck has a container neck wall having an externalscrew thread design for interlocking in mating relationship with theinternal screw thread design of the container cap wall and having anangle of an external threading to the container neck wall that isbetween approximately thirty degrees and approximately forty-fivedegrees. The thread form of the material savings container cap is alsounique and is described as the interlocking screw thread design from.The internal screw thread always points towards an inner surface of theflat top of the container cap and towards an axis of rotation of thecontainer cap. The associated container neck has a container neck wallthat has an external screw thread design for interlocking in matingrelationship with the internal screw thread design of the container capwall and wherein an external screw thread always points away from anopening of the container and away from an axis of rotation of thecontainer neck.

IMPORTANT OBJECTS AND ADVANTAGES

The following important objects and advantages of the present inventionare

-   -   (1) to provide a container cap and associated container neck        that is economical;    -   (2) to provide material saving in the container cap    -   (3) to provide a container cap having segments    -   (4) to provide such a cap that does not have a complete cylinder        of material that contains the internal threading    -   (5) to provide such a cap that is of the interlocking screw        thread design form    -   (6) to provide such a cap that has spaces between segments of        material on the container wall such that the spaces plus the        segments form the complete cylinder of material that is        characteristic of caps that are not of the material saving cap        design.    -   (7) To provide such a cap which results in the saving of between        5% and 40% material savings compared to caps that are not of the        material saving design.    -   (8) To provide a container cap and container neck container        combination wherein the container cap has spaces in its        container wall and has a unique threading    -   (9) To provide a container cap having an internal screw thread        having an angle in the range of between approximately thirty        degrees and approximately forty-five degrees between the thread        and the cap wall    -   (10) To provide such a cap wherein the internal threading of the        cap and the external threading of the container neck are such as        to create a ratchet type locking effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the container cap of the present inventionscrewed on to its associated container neck showing three segments.

FIG. 2 is a cross-sectional view of the preferred embodiment of theexternal (container neck) interlocking screw thread design

FIG. 3 is a cross-sectional view of the preferred embodiment of theinternal (container cap) interlocking screw thread design

FIG. 4 is a cross-sectional view of an alternative embodiment of theexternal (container neck) interlocking screw thread design

FIG. 5 is a cross-sectional view of an alternative embodiment of theinternal (container cap) interlocking screw thread design

FIG. 6 is a cross-sectional view of the alternative embodiment of thecombined internal and external interlocking screw thread design shownseparately in FIGS. 4 and 5 wherein the combined container cap andassociated container neck is depicted

FIG. 7 is an enlarged fragmentary cross-sectional view of thealternative embodiment of the combined internal and externalinterlocking screw thread design showing the mating threads.

FIG. 8 is a horizontal cross-section of the container cap of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings the material savings container cap comprises acircular flat top which is a flat disk of variable thickness andconsists of an exposed upper surface 1 and an enclosed inner surface 2.The area of physical contact between the enclosed inner surface and therim of the associated container neck 14 forms the seal. The segments3,9,10,46,50 are perpendicular extensions of the inner surface area ofthe material savings container cap and point away from it. The uniquesegments are separated by spaces. An example of a space, is the areabounded by the dashed lines 48,49 and the segments 46,50. The segmentsand spaces together form a complete cylinder in cross-section as shownin FIG. 8. The wall thickness of this cylinder is equal to the thicknessof any segment. This cylinder consists of real and imaginary parts. Thereal parts are the segments. The imaginary parts are the spaces. Capsnot of the material savings design do not have spaces but insteadconsist of a complete hollow cylinder of material. The wall of thishollow cylinder is located in the region that contains thread or threadsand is used to support these thread or threads. The complete cylinder ofthe material savings cap has an axis of rotation that passes through thecenter of the circular flat top of the material savings container cap.The unique segments form an incomplete cylinder of material. The outersurface area of the segments merges into the circular flat top. Theradius of the circular flat top and the radius from the center ofrotation of any segment to the outer surface of its wall is equal. Thepresence of raised or recessed surfaces on the surface of the materialsavings cap are allowed. This is mainly for the purpose of productidentification and aesthetics.

There are two different segment arrangements. The first is the simplesegment arrangement. Here all the segments are of equal size andthickness and are arranged so that any reference point taken on any ofthe segments, makes the exact angle between that chosen point, thecenter of rotation of the segments and the same reference point on anadjacent segment. This all occurs in a plane parallel to that of thecircular flat top of the material savings container cap as shown in FIG.8. This angle is equal for every segment chosen for material savingscontainer caps that comply with the single segment arrangement. Thesimple segment arrangement provides for generally equal load sharingbetween all the segments. The angle between the segments is determinedby dividing 360 degrees by the required number of segments. The numberof segments for the simple segment arrangement is a range. This range isthe set of whole numbers from two to one hundred and are inclusive ofthese boundary values.

The second segment arrangement shall be known as the random segmentarrangement where there can be any variation in shape and size betweensegments for the purposes of product identification and aestheticreasons. Every point in space occupied by a segment is part of thestanding walls of a cylinder. The wall thickness of this cylinder isequal to the thickness of any segment, since all the segments of anymaterial savings cap are of equal thickness. The axis of rotation ofthis cylinder passes through the center of the circular flat top of thematerial savings container cap. The axis of rotation is perpendicular tothe circular flat top. Each segment of the random segment arrangement isattached to and merges into the circular flat top. A variation in sizeand or shape of segments results in a change in surface area betweensegments that are different. The maximum holding force is directlyproportional to the inner surface area of the segments. The innersurface area of a segment is that surface that is nearest to the axis ofrotation.

The segment range of any material savings container cap will varyaccording to size of the cap, material used and the forces involved. Thenumber of segments for the random segment arrangement is a range. Thisrange is the set of whole numbers from two to one hundred and areinclusive of these boundary values.

The thread/threads of the material savings container cap go on the innersurface of the segments 3,10 and point up towards the material savingscontainer cap's top. The thread/threads of the material savingscontainer cap also point towards the axis of rotation of the materialsavings container cap. The thread/threads merge into the inner surfaceof the segments as shown in segments 3,10. The diameter of the imaginarycylinder bound by the inner surface of the segments and minus thethread/threads, is the major diameter of the material savings containercap. This is the same as twice the perpendicular distance between theaxis of rotation 15 and the root of the thread 16. The thread/threadsrun along the imaginary cylinder whose inner surface diameter is themajor diameter of the material savings container cap. The thread/threadsoccur only on those sections of the imaginary cylinder that coincidewith the segments on the material savings container cap. Therefore thethread/threads occur only in those areas where the segments form realsections of the imaginary cylinder. The thread/threads of the materialsavings container cap is/are of the internal interlocking screw threaddesign forms whereas the thread/threads of the associated container neckis/are of the external interlocking screw thread design forms. Theremust be the same number of threads on the material savings container capand its associated container neck 8. The associated container neck iscylindrical in form with its rim perpendicular to the axis of rotationof the associated container neck. It has a specific wall thicknessthroughout which is dependant upon customer requirements and materialsused to manufacture it. The thread/threads on the material savingscontainer cap start on any of the segments below the inner surface ofthe material savings container cap's top.

These thread/threads have the same axis of rotation as that describedpreviously for the segments of the material savings container cap. Themajor diameter of the material savings container cap contains the rootof the thread/threads. This therefore implies that the root of eachthread for the material savings container cap of the basic internalinterlocking screw thread design form is the inner segment surface only.Each thread of the material savings container cap is comprised of bothimaginary and real sections. The real sections of the thread/threads arethose sections that exist in segments. The imaginary sections of athread are those regions of that thread that join the real sections ofthat thread together forming the characteristic helical curve of athread. The position of the thread/threads for each segment is exactlythe same as the position of the thread/threads section on that part ofthe imaginary cylinder which represents that particular segment.

The thread/threads of the associated container neck go on its externalsurface. These thread/threads are located below the rim of theassociated container neck. The external interlocking screw thread designforms of the associated container neck of the material savings containercap always points away from the rim of the associated container neck. Inaddition the thread/threads also point away from the axis of rotation ofthe associated container neck. The cylinder wall of the associatedcontainer neck ends at the top in a plane perpendicular to the axis ofrotation of the associated container neck.

The diameter of the external surface of the associated container neckminus the thread/threads is known as the minor diameter of theassociated container neck. This diameter is taken in any planeperpendicular to the axis of rotation of the associated container neck.The minor diameter of the associated container neck is equal to twicethe perpendicular distance between the axis of rotation 19 and the rootof the thread 21. The thread/threads is/are continuous unlike thethread/threads on the material savings container cap which areintermittent.

The thread/threads of the associated container neck have correspondingthread/threads on the complimentary material savings container cap thatmate with these thread/threads. The thread/threads of the materialsavings container cap and associated container neck fit togethercreating a unique interlocking effect. This interlocking between threadsprevents movement or bending of the segments away from the axis ofrotation when tightened onto its corresponding associated containerneck.

The minor diameter of the associated container neck and the majordiameter of the corresponding material savings container cap aredimensioned so as to allow for the required amount of clearance afterthe thread size is chosen. The fit between internal and external matingthreads is dependant on the allowance given between these threads onassembly. The fit of the mating parts is dependant on customerrequirements.

The interlocking screw thread design form is a unique thread form inform and function. The first unique feature of the interlocking screwthread design form is the orientation of the mating threads of thematerial savings container cap and the associated container neck. Thethread/threads on the material savings container cap always point to thecircular flat top whereas the thread/threads on the associated containerneck always point away from the rim of the associated container neck.The thread/threads on the associated container neck always point awayfrom the axis of rotation whereas the thread/threads on the materialsavings cap always point towards the axis of rotation. The assembly ofthe material savings container cap and associated container neck incross section emphasize the importance of orientation of these threadsin providing this locking force.

The second unique feature is the type of interlocking that occurs. Thiscan be most clearly described by stating the maximum number of threadsurfaces cut by a line 45 perpendicular to the axis of rotation 19 ofmating threads of the rounded external and internal interlocking screwthread design forms 43,44. The surfaces cut by this line 45 are asfollows:

-   -   The real rounded root of the rounded internal interlocking screw        thread    -   The real crest of the rounded external interlocking screw thread    -   The real primary flank of the rounded external interlocking        screw thread    -   The real primary flank of the rounded internal interlocking        screw thread    -   The real crest of the rounded internal interlocking screw thread    -   The real rounded root of the rounded external interlocking screw        thread

The maximum total number of surfaces cut by a line perpendicular to theaxis of rotation and midway along the mating threads of any of theexternal and internal interlocking screw thread design forms are sixsurfaces. The maximum total number of surfaces cut by a lineperpendicular to the axis of rotation and midway along the matingthreads of any thread forms other than that of the external and internalinterlocking screw thread design forms are two surfaces.

The Interlocking Screw Thread Design Form

The interlocking screw thread design form is divided into the externaland internal interlocking screw thread design forms. The external andinternal interlocking screw thread design forms are each further dividedinto two sub categories. The first is the basic external interlockingscrew thread design form and the rounded external interlocking screwthread design form. The second is the basic internal interlocking screwthread design form and the rounded internal interlocking screw threaddesign form.

These thread design forms are best explained by examination ofcross-sectional views of a material savings cap and its complimentaryassociated container neck. Each view is taken in a plane along thediameter of the material savings cap or associated container neck. FIGS.2 to 6 show only half of that view since it contains all the relevantparts required for the description of a thread. A developmental approachshall be taken in the description of these thread forms.

The basic external interlocking screw thread design form is outlined inFIG. 2. A line is constructed parallel to the axis of rotation 19. Theperpendicular distance between this construction line and the axis ofrotation is half of the minor diameter of the associated container neck.The construction line contains the distance x which is the width of thethread and is measured in a direction parallel to the axis of rotation.The variable x is a measure of length and can be either metric orEnglish units provided the chosen unit of length is maintainedthroughout. The width x is proportional to the holding force of thethread since it is directly related to thread size, however there areother determining factors. These factors are first physical data on thematerial type chosen in the manufacture of the associated containerneck. Second is the maximum closing forces placed on the materialsavings cap and associated container neck assembly.

All threads of the basic external interlocking screw thread design formmust adhere to the following constraints.

The flanks begin on either side of the distance x and extend away fromit and the axis of rotation 19. The secondary flank 55 is that side ofthe thread that is closest to the opening of the associated containerneck. The smallest angle the secondary flank makes with the distance xmust be between 30 and 45 degrees and includes these boundary values.This angle is measured in a counter-clockwise direction from the axis ofrotation. The angle shall be denoted by the variable α. The primaryflank 52 is the side of each thread that is furthest away from theopening of the associated container neck. The primary flank is equal inlength and parallel to the secondary flank. The flank length is measuredparallel to the flank. The flank length shall be denoted by the variableF. The greatest length a flank of the basic external interlocking screwthread design form can have is 3x. The least length a flank of the basicexternal interlocking screw thread design form can have is 0.3x.

The crest of a thread is flat and parallel to the axis of rotation. Thewidth of the thread of the basic external interlocking screw threaddesign form is uniform throughout therefore the crest width is equal tox.

The height of a thread is measured in a direction perpendicular to theaxis of rotation of that thread. The height of a thread is the distancebetween the crest and the root of that thread. The height shall bedenoted by the variable H. The height is given by the formula H=F(sinα). The greatest height is directly proportional to the greatest flanklength 3x and is shown in FIG. 2 by the perpendicular distance betweenthe crest 20 and the root 21. The least height is directly proportionalto the least flank length 0.3x and is shown by the perpendiculardistance between the dashed line 22 and the root 21. The dashed line 22depicts a region in space and is not the crest of the thread in FIG. 2.

The root 21 is the space between adjacent crests. The root width is ameasure of that distance between threads at their base and is parallelto the axis of rotation. The root is also part of the construction linereferred to in the description of x. The root shall be denoted by thevariable R. The root is given by the formula R=x+y where y is the set ofpositive real numbers from 0 to 5x and is inclusive of these boundaryvalues. The variable y provides for clearance between mating threads.

The description above for the basic external interlocking screw threaddesign form, with reference to FIG. 2 provides for an area within whichthe thread can exist. This area cannot exist for a thread height thatfalls outside this boundary area. This boundary area is enclosed by thesecondary flank 55, the primary flank 52, the least crest height of athread 22, the greatest crest height of a thread 20.

The basic internal interlocking screw thread design form is outlined inFIG. 3. All threads of the basic internal interlocking screw threaddesign form must adhere to the following constraints.

A line is constructed parallel to the axis of rotation of the materialsavings cap 15. The perpendicular distance between this constructionline and the axis of rotation 15 is the major radius or half of themajor diameter of the material savings cap. This distance is determinedby the formula ½D¹=(D+γ)½ where D¹ is the major diameter of the materialsavings cap, D is the minor diameter of the associated container neckand γ is a real positive number that is no greater than ½H. The value γprovides for clearance between the mating threads when the materialsavings cap is screwed onto its associated container neck.

The variable x remains the same for the thread width of the basicexternal and internal interlocking screw thread design forms and lies onthe construction line mentioned previously for the basic internalinterlocking screw thread design form.

The flanks of the thread begin on either side of the distance x. Theflanks extend away from x and towards the axis of rotation 15. Theprimary and secondary flanks of the basic internal interlocking screwthread design form are parallel to each other. The angle the flanks ofthe thread make relative to the axis of rotation shall be known as β.This angle is measured in a counter-clockwise direction relative to theaxis of rotation 15. The formula for this new angle is β=180+α. Thelength of the flanks F is the same as that chosen for the basic externalinterlocking screw thread design form. Therefore the same limits offlank length apply. The flank length therefore falls within the range0.3x to 3x and is inclusive of these boundary values. The primary flank53 is the side of the thread that is closest to the inner surface of thecircular flat top of the material savings cap. The secondary flank 54 isthat side of the thread that is furthest away from inner surface of thecircular flat top of the material savings cap. The arrow on the axis ofrotation 15 points to the circular flat top of the material savings cap.

The thread height of the basic internal interlocking screw thread designform is a measure of the perpendicular distance between the crest andthe root of the thread. This height is equal to H the height of thebasic external interlocking screw thread design form. The crest isparallel to the axis of rotation 15 and is equal to x when measured in adirection parallel to the axis of rotation. The root 16 is the spacebetween adjacent primary and secondary flanks. The root width isparallel to the axis of rotation 15. The root width is the same as thatfor the basic external interlocking screw thread design form and isequal to R.

The dashed line 18 represents the crest position that has the leastheight allowed by the basic internal interlocking screw thread designform. The crest 17 represents the crest position that has the greatestheight allowed by the basic internal interlocking screw thread designform. The description above for the basic internal interlocking screwthread design form, with reference to FIG. 3 provides for an area withinwhich the thread can exist. The thread cannot exist if the height of thethread causes it to fall outside this boundary area. The boundary areaof FIG. 3 is the secondary flank 54, the primary flank 53, the leastcrest height 18, and the greatest crest height 17.

The internal interlocking screw thread design form can also be looked atas two reflections of the external interlocking screw thread designform. The first reflection occurs with the mirror line as the axis ofrotation. This is followed by a second reflection along a mirror linethat is perpendicular to the axis of rotation 19. This mirror line doesnot cut any of the thread surfaces. The axis of rotation changes and islocated by the formula ½D¹=(D+γ)½ to the new position 15.

The pitch of the basic internal and external interlocking screw threaddesign forms are equal. The pitch shall be denoted by the symbol p. Theformula for the pitch is p=2x+y.

The rounded external and internal interlocking screw thread design formsare a further development on the basic external and internalinterlocking screw thread design forms.

The rounded external interlocking screw thread design form is outlinedin figure 4. The rounded external interlocking screw thread design formis made up of real and imaginary parts. The imaginary parts areconstruction lines which are used to determine where the real parts ofthe thread lie. The profile of the basic external interlocking screwthread design form is shown in FIG. 4 by the crest 20, the secondaryflank, the primary flank 6, 29,26 and the root 37,38. The secondaryflank 55 (of the basic external interlocking screw thread design form)is not numbered in FIG. 4 since the difference between this and the realsecondary flank 7 (of the rounded external interlocking screw threaddesign form) is very small and not visible in FIG. 4. The basic externalinterlocking screw thread design form is the framework upon which therounded external interlocking screw thread design form is built around.

All threads of the rounded external interlocking screw thread designform must adhere to the following constraints. The determination of thethread width x and its position relative to the axis of rotation 19 arethe same as that for the basic external interlocking screw thread designform.

The flanks go on either side of the distance x as shown by the secondaryflank and the primary flank 26,6,29. The real primary flank 6 and realsecondary flank 7 of the rounded external interlocking screw threaddesign form are always parallel to each other but are not equal inlength. The greatest real secondary flank 7 is not equal to the greatestsecondary flank 55 of the basic external interlocking screw threaddesign form. The angle the flanks make with the distance x measured in acounter clockwise direction is α. This angular constraint is the same asthat for the basic external interlocking screw thread design form.

The height H of the real crest 24 is the perpendicular distance betweenthe imaginary part 20 (of the crest) and real flat root 38 of therounded external interlocking screw thread design form. The height ofthe rounded external interlocking screw thread design form is measuredin the same way as that for the basic external interlocking screw threaddesign form H. The crest of the rounded external interlocking screwthread design form consists of a real and imaginary part. The real crest24 of the rounded external interlocking screw thread design form isshown. The imaginary part is shown as 20 and is the crest for the basicexternal interlocking screw thread design form. The real crest 24 of therounded external interlocking screw thread design form, in FIG. 4 is themaximum crest height that can exist for the rounded externalinterlocking screw thread design form.

The real crest 24 of the rounded external interlocking screw threaddesign form is different to that of the basic external interlockingscrew thread design form and is derived as follows. A construction line25 is drawn so that it divides the angle between the lines 20 and 26 inhalf. A construction line 23 is then drawn that connects theconstruction line 25 with the junction where the secondary flank (of thebasic external interlocking screw thread design form) meets theconstruction line 20. This connection is such that the angle formedbetween the construction lines 23 and 25 is 90 degrees. The junctionwhere the construction line 23 and 25 meet is the center point of thearc 24. The diameter of the arc 24 is equal to the perpendiculardistance between the real primary flank 6 and real secondary flank 7.This distance is taken perpendicular to either flank since they areparallel to each other. This also implies that the center of the arc 24lies along a line. This line is parallel to either flank and midwaybetween the flanks. The arc 24 merges into the secondary flank 7 andprimary flank 6.

The real rounded root 39 of the rounded external interlocking screwthread design form is dependent on the real crest 31 of the roundedinternal interlocking screw thread design form. The dashed lines in FIG.5 indicate construction lines.

The basic internal interlocking screw thread design form is shown inFIG. 5 by the primary flank 33,4,36 ,the secondary flank, the crest 17and the root 41,40. The secondary flank 54 (of the basic internalinterlocking screw thread design form) is not numbered in FIG. 5 sincethe difference between this and the real secondary flank 5 (of therounded internal interlocking screw thread design form) is very smalland not visible in FIG. 5.

The thread width of the rounded external and internal interlocking screwthread design forms are equal. The primary and secondary flanks begin oneither side of the distance x. The distance x is parallel to the axis ofrotation of the material savings cap. The perpendicular distance betweenthe axis of rotation 15 and the distance x is given by the formula½D¹=(D+γ)½ where D¹ is the major diameter of the material savings cap, Dis the minor diameter of the complimentary associated container neck andγ is a real positive number that is no greater than ½H. This is the samecondition as that for the basic internal interlocking screw threaddesign form.

The primary flank lengths of the rounded external and internalinterlocking screw thread design forms are equal. The secondary flanklengths of the rounded external and internal interlocking screw threaddesign forms are also equal. The primary and secondary flanks of therounded internal interlocking screw thread design form are parallel toeach other. The primary flank 4,33,36 consists of real and imaginaryparts. The real primary flank 4 and the real secondary flank 5 of therounded internal interlocking screw thread design form are shown in FIG.5. The angle the flanks of the thread make relative to the axis ofrotation shall be known as β. This angle is measured in acounter-clockwise direction relative to the axis of rotation 15. Theformula for this new angle is β=180+α. This angle is the same as thatfor the basic internal interlocking screw thread design form. The heightof the thread of the rounded internal interlocking screw thread designform is equal to H. H is measured in the same way as that for therounded external interlocking screw thread design form. The height H ofthe thread is the same as that height for the complimentary thread ofthe rounded external interlocking screw thread design form.

The crest of the rounded internal interlocking screw thread design formconsist of real and imaginary parts. The real part shall be known as thereal crest 31 of the rounded internal interlocking screw thread designform. The imaginary part 17 of the rounded external interlocking screwthread design form is the crest of the basic internal interlocking screwthread design form. The real crest 31 of the rounded internalinterlocking screw thread design form is different to that of the basicinternal interlocking screw thread design form and is derived asfollows. A construction line 32 is drawn so that it divides the anglebetween the lines 17 and 33 in half. A construction line 30 is thendrawn that connects the construction line 32 with the junction where thesecondary flank (of the basic internal interlocking screw thread designform) meets the construction line 17. This connection is such that theangle formed between the construction lines 30 and 32 is 90 degrees. Thejunction where the construction lines 30 and 32 meet is the center pointof the arc 31. The diameter of the arc 31 is equal to the perpendiculardistance between the real primary flank 4 and real secondary flank 5 ofthe rounded internal interlocking screw thread design form. Thisdistance is taken perpendicular to either flank since they are parallelto each other. This also implies that the center of the arc 31 liesalong a line. This line is parallel to either flank and midway betweenthe flanks. The arc 31 merges into the real secondary flank 5 and realprimary flank 4 of the rounded internal interlocking screw thread designform.

The conditions are now set to determine the structure of the root of therounded external interlocking screw thread design form shown in FIG. 4.The following construction lines 33,32,17,30,31 of FIG. 4 shows themating of this region of the rounded internal interlocking screw threaddesign form with the rounded external interlocking screw thread designform. The perpendicular distance between the construction lines 17 and37 is equal to ½γ. The perpendicular distance between construction lines29 and 33 is also equal to ½γ. This means that the perpendicular offsetdistance for the mating primary flanks of the rounded internal andexternal interlocking screw thread design forms are equal to ½γ. Thisalso means that the perpendicular offset distance for the mating crestsof the rounded internal and external interlocking screw thread designforms are equal to ½γ. The axis of rotation 19 shown in FIG. 4 is thesame axis of rotation for the rounded internal interlocking screw threaddesign form parts shown in this figure. The root of the rounded externalinterlocking screw thread design form is made up of real and imaginaryparts. The real parts are the real rounded root 39 of the roundedexternal interlocking screw thread design form and the real flat root 38of the rounded external interlocking screw thread design form. Theimaginary part of the root of the rounded external interlocking screwthread design form 37 is part of the root of the basic externalinterlocking screw thread design form. The real rounded root of therounded external interlocking screw thread design form is formed asfollows. The center of rotation of the arc 39 is located at the centerof rotation of the arc 31 in FIG. 4. The arc 39 merges into the realflat root 38 and the real primary flank 6. The root length of therounded external interlocking screw thread design form is equivalent tothat of the basic external interlocking screw thread design form. Thisis given by the formula R=x+y where in this case y must always begreater than ½γ. The new range of y is from ½γ to 5x and does notinclude the lower boundary value.

The arc 27 shown in FIG. 4 depicts the minimum real crest height of thethread of the rounded external interlocking screw thread design form.The center of this arc 27 is located along a line. This line is parallelto the real secondary flank 7 and midway between the real primary flank6 and real secondary flank 7 of the thread. The diameter of this arc isthe perpendicular distance between the real primary and real secondaryflanks of the rounded external interlocking screw thread design form.The location of the arc is determined by the construction of a lineperpendicular to the axis of rotation that originates from the center ofthe arc 39 and extends away from the axis of rotation 19. Thisconstruction line is 28 in FIG. 4. The arc is tangential to theconstruction line 28, the real secondary flank 7 and the real primaryflank 6 and merges into these surfaces.

The rounded external interlocking screw thread design form shown in FIG.4 shows the boundary area where the thread can exists. This area isbounded by the arc 24 (or real crest), the arc 27, the real secondaryflank 7 and the real primary flank 6.

The root of the rounded internal interlocking screw thread design formis made up of real and imaginary parts. The real parts are the realrounded root 42 and the real flat root 41 of the rounded internalinterlocking screw thread design form.

The imaginary part of the root of the rounded internal interlockingscrew thread design form 40 forms part of the root of the basic internalinterlocking screw thread design form. The real rounded root of therounded internal interlocking screw thread design form is formed asfollows. The center of rotation of the arc 42 is located at the centerof rotation of the arc 24 in FIG. 5. The arc 42 merges into the realflat root 41 and the real primary flank 4. The root length of therounded internal interlocking screw thread design form is equivalent tothat of the basic internal interlocking screw thread design. This isgiven by the formula R=x+y where in this case y must always be greaterthan ½γ. The new range of y is from ½γ to 5x and does not include thelower boundary value.

The arc 35 shown in FIG. 5 depicts the minimum real crest height of thethread of the rounded internal interlocking screw thread design form.The center of this arc 35 is located along a line. This line is parallelto the real secondary flank 5 and midway between the real primary flank4 and real secondary flank 5 of the thread. The diameter of this arc isthe perpendicular distance between the real primary and real secondaryflanks of the rounded internal interlocking screw thread design form.The location of the arc 35 is determined by the construction of a line34 (see FIG. 5) perpendicular to the axis of rotation that originatesfrom the center of the arc 42 and extends toward the axis of rotation15. The arc 35 is tangential to the construction line 34, the realsecondary flank 5 and the real primary flank 4 and arc 35 merges intothese surfaces. The perpendicular distance between the constructionlines 20 and 40 is equal to ½γ. The perpendicular distance betweenconstruction lines 26 and 36 is also equal to ½γ. This means that theperpendicular offset distance for the mating primary flanks of therounded internal and external interlocking screw thread design forms areequal to ½γ. This also means that the perpendicular offset distance forthe mating crests of the rounded internal and external interlockingscrew thread design forms are equal to ½γ. The location of the arc isdetermined by the construction of a line perpendicular to the axis ofrotation that originates from the center of the arc 42 and extendstowards the axis of rotation 15. This construction line is 34 in FIG. 5.The arc is tangential to the construction line 34, the real secondaryflank 5 and the real primary flank 4 and merges into these surfaces. Therounded internal interlocking screw thread design form shown in FIG. 5shows the boundary area where the thread can exists. This area isbounded by the arc 31 (or real crest), the arc 35, the real secondaryflank 5 and the real primary flank 4.

The mating of the threads of the rounded external and internalinterlocking screw thread design forms is shown in FIG. 6. FIG. 6 showsthe relevance of the respective construction lines in the development ofthe rounded external and internal interlocking screw thread designforms. In addition it also shows the mating of the basic external andinternal interlocking screw thread design forms when the outline ofthese thread design forms is deciphered from the solid and dashed lines.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the material savings cap screwed onto its associatedcontainer neck. This view is a side view looking along a line thatenters perpendicularly into the page and center of segment 9. Segment 9is perpendicular to this line of view and is in a direction parallel tothe axis of rotation of the material savings cap. The dashed lines inthe figure represent details that are hidden from view. The materialsavings cap is of the simple segment arrangement and is comprised offour segment. Only three segments 3, 9, 10 are shown in the drawing. Thefourth is hidden from view and located on the opposite side of segment9. The threads on the material savings cap are of the rounded internalinterlocking screw thread design form. The angle α chosen for the flanksof the rounded external interlocking screw thread design form is 45degrees, the width of the thread is x, the root R=1¼x, the pitch=2¼x,½γ=0.05x.

The associated container neck is shown by 8. The threads of theassociated container neck are of the rounded external interlocking screwthread design form. The real primary flank 4 and the real secondaryflank 5 of the rounded internal interlocking screw thread design formare shown. The real primary flank 6 and the real secondary flank 7 ofthe rounded external interlocking screw thread design form are shown.The lines 11, 12 and 13 were introduced to provide a better perspectiveof the cylindrical shape of the associated container neck. These linesrepresent boundary regions or junctions of the thread. The line 11represents the junction where the real crest of the rounded externalinterlocking screw thread design form becomes hidden from view. The line13 represents the junction between the real crest and the real secondaryflank of the rounded external interlocking screw thread design formmeet. The line 12 represents the boundary between the real secondaryflank of the rounded external interlocking screw thread design form andthe external surface of the associated container neck meet. The rim ofthe associated container neck 14 is shown. The upper surface 1 and theenclosed inner surface 2 of the circular flat top are shown.

FIGS. 2 and 3 complement one another in the sense that FIG. 2 shows theexternal thread on the neck whereas FIG. 3 shows the internal thread onthe cap.

FIG. 2 shows a cross-sectional view of the basic external interlockingscrew thread design form. The view is taken by cutting along a planethat contains and is parallel to a diameter of the associated containerneck. This plane also contains the axis of rotation 19 and is parallelto it and the plane is also perpendicular to the enclosed surface offlat top 2. FIG. 2 thus represents the view one sees when facing theplane of that cut. The view of FIG. 2 shows only half of the actualcross-section. In addition the view shows only a little more than twopitch lengths of thread. The half shown in FIG. 2 is that half above theaxis of rotation 19 of the associated container neck. The angle α notshown in FIG. 2 is equal to 30 degrees. This is the angle a flank makeswith the axis of rotation when measured in a counter clockwisedirection. The arrow at the end of the axis of rotation points in thedirection of the rim of the associated container neck. The secondaryflank 55 and the primary flank 52 are equal to 3x in length. Theseflanks are parallel to each other. The maximum crest 20 and the minimumcrest 22 are shown and are equal in length. The minimum crest 22 isshown by a dashed line ,and only indicates the position where theminimum crest would occur. The crests are parallel to the axis ofrotation and each has a length denoted by the variable x. The root 21 isparallel to the axis of rotation 19 and has a length denoted by theformula R=x+y. The value for y in FIG. 2 was chosen as x. Therefore inthis case R=2x.

FIG. 3 shows a cross-sectional view of the basic internal interlockingscrew thread design form. The view is taken by cutting along a planethat contains and is parallel to a diameter of the material savings cap.This plane contains the axis of rotation 15 and is parallel to it. FIG.3 thus represents the view one sees when facing the plane of that cut.The view of FIG. 3 shows only half of the actual cross-section. The halfshown is that half above the axis of rotation 15 of the material savingscap. The view shows only a little more than two pitch lengths of thread.The diagram of FIG. 3 is dependent on dimension and angles chosen forFIG. 2 since it complements the latter. The angle β not shown in FIG. 2is equal to 210 degrees and is derived from the formula β=α+180, where αfor the complimentary associated container neck in FIG. 2 was chosen as30 degrees. This is the angle a flank makes with the axis of rotation 15when measured in a counter clockwise direction. The arrow at the end ofthe axis of rotation points in the direction of the circular flat top ofthe material savings cap. The secondary flank 54 and the primary flank53 are equal to 3x in length. This length is equal to the length chosenfor a flank in FIG. 2 which is the complimentary associated containerneck. The primary flank 53 is parallel to the secondary flank 54. Themaximum crest height of FIG. 2 is equal to the maximum crest height inFIG. 3. The minimum crest height of FIG. 2 is equal to the minimum crestheight of FIG. 3. The maximum crest 17 and the minimum crest 18 areshown and are equal in length. The minimum crest 18 is shown by a dashedline and only indicates the position where the minimum crest wouldoccur. The crests are parallel to the axis of rotation and each has alength of x. The root 16 is parallel to the axis of rotation 15 and hasa length denoted R=2x which is derived from its complimentary associatedcontainer neck in FIG. 2.

FIG. 4 shows a cross-sectional view of the rounded external interlockingscrew thread design form. The view is taken by cutting along a planealong a diameter of the associated container neck. This plane containsthe axis of rotation 19 and is parallel to it. FIG. 4 thus representsthe view one sees when facing the plane of that cut. The view of FIG. 4shows only half of the actual cross-section In addition the view of FIG.4 shows only a little more than two pitch lengths of thread. The halfshown is that half above the axis of rotation 19 of the associatedcontainer neck.

The basic external interlocking screw thread design form of FIG. 2 isshown in FIG. 4. The crest 20, the primary flank 26,6,29, the secondaryflank and the root 37, 38 of the basic external interlocking screwthread design form of FIG. 2 are shown. The secondary flank 55 of FIG. 2is not numbered in FIG. 4. This is because the difference between thesecondary flank 55 and the real secondary flank 7 of the (roundedexternal interlocking screw thread design form) is so small that it isnot visible in FIG. 4. The following information can be inferred fromFIG. 2. The angle α not shown in FIG. 4 is equal to 30 degrees. This isthe angle a flank makes with the axis of rotation when measured in acounter clockwise direction. The arrow at the end of the axis ofrotation points in the direction of the rim of the associated containerneck. The crest 20 is parallel to the axis of rotation and has a lengthdenoted by the variable x. The root is parallel to the axis of rotation19 and has a length of 2x.

The rounded external interlocking screw thread design form is composedof real and imaginary parts. The imaginary parts are construction lineswhich are used to determine where the real parts of the thread lie. Theconstruction lines are shown by dashed lines in FIG. 4. The primaryflank 26,6,29 is divided into the real primary flank 6 and the imaginarypart 26,29 of the rounded external interlocking screw thread designform. The real secondary flank 7 of the rounded external interlockingscrew thread design form is shown. The crest is divided into the realcrest 24 and the imaginary part 20 of the rounded external interlockingscrew thread design form. The root is divided into the real rounded root39, the real flat root 38 and the imaginary part 37 of the roundedexternal interlocking screw thread design form. The construction lines33,32,17,31,30,28 are derived from the rounded internal interlockingscrew thread design form of FIG. 5 and are positioned where the threadswould mate. The axis of rotation of these construction lines is also theaxis of rotation 19. The construction line 28 originates from the centerof the arc 31 and is perpendicular to the axis of rotation 19. Theminimum real crest height 27 is located tangential and merges into thereal secondary flank 7, the real primary flank 6 and the constructionline 28.

The construction line 25 is drawn so that it divides the angle betweenthe construction lines 26 and 20 in half. A construction line 23 is thendrawn that connects the construction line 25 with the junction where thesecondary flank (of the basic external interlocking screw thread designform) meets the construction line 20. The angle formed between theconstruction lines 23 and 25 is 90 degrees.

FIG. 5 shows a cross-sectional view of the rounded internal interlockingscrew thread design form. The view is taken by cutting along a planealong a diameter of the material savings cap. This plane contains theaxis of rotation 15 and is parallel to it. FIG. 5 thus represents theview one sees when facing the plane of that cut The view of FIG. 5 showsonly half of the actual cross-section. In addition the view shows only alittle more than two pitch lengths of thread. The half shown is thathalf above the axis of rotation 15 of the material savings cap. Thebasic internal interlocking screw thread design form of FIG. 3 is shownin FIG. 5. The crest 17, the primary flank 33,4,36, the secondary flankand the root 40,41 of the basic internal interlocking screw threaddesign form of FIG. 3 are shown. The secondary flank 54 of FIG. 3 is notnumbered in FIG. 5. This is because the difference between the secondaryflank 54 and the real secondary flank 5 of the (rounded internalinterlocking screw thread design form) is so small that it is notvisible in FIG. 5. The following information can be inferred from FIG.3.The angle β not shown in FIG. 5 is equal to 210 degrees. This is theangle a flank makes with the axis of rotation when measured in a counterclockwise direction. The arrow at the end of the axis of rotation pointsin the direction of the circular flat top. The crest 17 is parallel tothe axis of rotation and has a length denoted by the variable x. Theroot is parallel to the axis of rotation 15 and has a length of 2x.

The rounded internal interlocking screw thread design form is composedof real and imaginary parts. The imaginary parts are construction lineswhich are used to determine where the real parts of the thread lie. Thedashed lines are construction lines in FIG. 5. The primary flank 33,4,36is divided into the real primary flank 4 and the imaginary parts 33,36of the rounded internal interlocking screw thread design form. The realsecondary flank 5 of the rounded internal interlocking screw threaddesign form is shown. The crest is divided into the real crest 31 andthe imaginary part 17 of the rounded internal interlocking screw threaddesign form. The root is divided into the real rounded root 42, the realflat root 41 and the imaginary part 40 of the rounded internalinterlocking screw thread design form. The construction lines20,26,25,23,24,34 are derived from the rounded external interlockingscrew thread design form of FIG. 4 and are positioned where the threadswould mate. The axis of rotation of these construction lines is also theaxis of rotation 15. The construction line 34 originates from the centerof the arc 24 and is perpendicular to the axis of rotation 15. Theminimum real crest height 35 is located tangential and merges into thereal secondary flank 5, the real primary flank 4 and the constructionline 34.

The construction line 32 is drawn so that it divides the angle betweenthe construction lines 17 and 33 in half. A construction line 30 is thendrawn that connects the construction line 32 with the junction where thesecondary flank (of the basic internal interlocking screw thread designform) meets the construction line 17. The angle formed between theconstruction lines 30 and 32 is 90 degrees.

FIG. 6 shows a cross-sectional view of the mating threads of the roundedinternal and external interlocking screw thread design forms. The viewis taken in a plane along a diameter of the material savings cap andassociated container neck. This plane contains the axis of rotation 19and is parallel to it. The view of FIG. 6 shows only half of the actualcross-section. The half shown is that half above the axis of rotation 19of the material savings cap and complimentary associated container neck.This view shows only a little more than two pitch lengths of thread.This view is used to show the numbered items and the relevance of theseitems when compared to FIGS. 4 and 5. The dashed lines are constructionlines in FIG. 6. The thread width is x. The flank length is 2.4x. Theangle α=30 degrees for the rounded external interlocking screw thread.The angle β=210 degrees for the rounded internal interlocking screwthread. The root width R=2x. The pitch=3x and ½γ=0.05x.

FIG. 6 is used to emphasize the importance of the construction lines inthe determination of where the real rounded crests and real roundedroots of the rounded external and internal interlocking screw threadslie. The thread parts are the same as that detailed in FIGS. 4 and 5.

FIG. 7 shows a cross-sectional view of the mating threads of the roundedinternal and external interlocking screw thread design forms. The viewis taken in a plane along a diameter of the material savings cap andassociated container neck. This view contains the axis of rotation 19and is parallel to it. The view of FIG. 7 shows only half of the actualcross-section. The half shown is that half above the axis of rotation 19of the material savings cap and complimentary associated container neck.The rounded external interlocking screw thread 44 and the roundedinternal interlocking screw thread 43 are shown without the constructionlines used to derive them. The dashed line 45 is drawn perpendicular tothe axis of rotation and passes through the center of rotation of arcsthat form the real crests of the rounded external and internalinterlocking screw threads. The total number of surfaces cut by line 45are six. These surfaces are the following:

-   -   (i) The real rounded root of the rounded internal interlocking        screw thread;    -   (ii) The real crest of the rounded external interlocking screw        thread;    -   (iii) The real primary flank of the rounded external        interlocking screw thread;    -   (iv) The real primary flank of the rounded internal interlocking        screw thread;    -   (v) The real crest of the rounded internal interlocking screw        thread; and    -   (vi) The real rounded root of the rounded external interlocking        screw thread.

FIG. 8 shows a cross-section of the material savings cap. Thiscross-section is taken perpendicular to the axis of rotation and alongthe segments. There are four segments of the simple segment arrangementtwo of which are numbered 46, 50. The view of FIG. 8 shown is takenlooking into the page along the axis of rotation 15 of the materialsavings cap, the axis of rotation 15 being a point located at theintersection of lines 47 and 51 (and the axis of rotation 15 beingperpendicular to the page on which FIG. 8 appears). The axis of rotation15 extends perpendicularly out of the page. The internal interlockingscrew thread cannot be visibly distinguished from the view of FIG. 8.The dashed lines 47 and 51 all connect the same sides of all thesegments. The angle between the dashed line 51 the axis of rotation 15and the dashed line 47 is 90 degrees. All angles between the center ofrotation and enclosed between the dashed lines 47 and 51 are equal to 90degrees. The dashed lines 48 and 49 represent the spaces between thesegments.

Thus the present invention can be described as a material savingscontainer cap comprising a circular flat top having a perimeter, anannular segmented container cap wall, each separated segment ofcontainer cap wall descending from a different portion of the perimeterof the top, the container cap wall having an internal screw threaddesign for interlocking in mating relationship with a container wall ofa container neck wherein the angle of the internal threading to thecontainer cap wall is between approximately thirty degrees andapproximately forty-five degrees and wherein the internal screw threadalways points towards the inner surface of the flat top of the containercap and towards an axis of rotation of the container cap.

The present invention also encompasses a combination of a materialsavings container cap and a container neck, the container cap being asdescribed and the container neck having a container neck wall having anexternal screw thread design for interlocking in mating relationshipwith the internal screw thread design of the container cap wall andhaving an angle of the external threading to the container neck wallthat is between approximately thirty degrees and approximatelyforty-five degrees and wherein the external screw thread always pointsaway from the opening of the container and away from the axis ofrotation of the container neck.

The above characteristics of the threading creates a ratchet typelocking effect. Accordingly, the effective locking force of the materialsavings cap is just as great as the locking force of a cap having acontinuous cylindrical container wall with no segments separated byspaces. The unique segment sizes and arrangements follow pre-determinedpatterns that conform to the mechanical demand of strength andaesthetics.

It is to be understood that while the apparatus of this invention havebeen described and illustrated in detail, the above-describedembodiments are simply illustrative of the principles of the invention.It is to be understood also that various other modifications and changesmay be devised by those skilled in the art which will embody theprinciples of the invention and fall within the spirit and scopethereof. It is not desired to limit the invention to the exactconstruction and operation shown and described. The spirit and scope ofthis invention are limited only by the spirit and scope of the followingclaims.

1. A material savings container cap comprising a circular flat tophaving a perimeter, an annular segmented container cap wall, eachseparated segment of container wall descending from a different portionof the perimeter of the top, the container cap wall having an internalscrew thread design for interlocking in mating relationship with acontainer wall of a container neck wherein an angle of an internalthreading to the container cap wall is between approximately thirtydegrees and approximately forty-five degrees.
 2. The combination of amaterial savings container cap and a container neck, the container caphaving a circular flat top having a perimeter, an annular segmentedcontainer cap wall, each separated segment of container wall descendingfrom a different portion of the perimeter of the top, the container capwall having an internal screw thread design for interlocking with acontainer wall of the container neck wherein an angle of a threading tothe container cap wall is between approximately thirty degrees andapproximately forty-five degrees, the container neck having a containerneck wall having an external screw thread design for interlocking inmating relationship with the internal screw thread design of thecontainer cap wall and having an angle of an external threading to thecontainer neck wall that is between approximately thirty degrees andapproximately forty-five degrees.
 3. A material savings container capcomprising a circular flat top having a perimeter, an annular segmentedcontainer cap wall, each separated segment of container cap walldescending from a different portion of the perimeter of the top, thecontainer cap wall having an internal screw thread design forinterlocking in mating relationship with a container wall of a containerneck wherein an internal screw thread always points towards an innersurface of the flat top of the container cap and towards an axis ofrotation of the container cap.
 4. The combination of a material savingscontainer cap and a container neck, the container cap having a circularflat top having a perimeter, an annular segmented container cap wall,each separated segment of container cap wall descending from a differentportion of the perimeter of the top, the container cap wall having aninternal screw thread design for interlocking in mating relationshipwith a container wall of a container neck wherein an internal screwthread always points towards an inner surface of the flat top of thecontainer cap and towards an axis of rotation of the container cap, thecontainer neck having a container neck wall that has an external screwthread design for interlocking in mating relationship with the internalscrew thread design of the container cap wall and wherein an externalscrew thread always points away from an opening of the container andaway from an axis of rotation of the container neck.